COMPARISON OF INTRAOCULAR PRESSURE MEASURED BY NON-CONTACT TONOMETRY AND GOLDMANN APPLANATION TONOMETRY IN ADULTS: A HOSPITAL-BASED CROSS-SECTIONAL STUDY
DOI:
https://doi.org/10.48047/ded78n19Keywords:
Intraocular pressure; non-contact tonometry; Goldmann applanation tonometry; Bland–Altman analysis; method comparison; glaucoma screening; South IndiaAbstract
Background: Accurate measurement of intraocular pressure (IOP) is central to the detection and management of glaucoma. Goldmann applanation tonometry (GAT) remains the reference standard, but its requirement for corneal contact, topical anaesthesia and fluorescein, together with a theoretical risk of cross-infection, has prompted interest in non-contact tonometry (NCT) as a screening alternative. Agreement data from South Indian populations are limited. Objective: To assess the agreement between IOP measured by NCT and GAT in adult patients attending a tertiary care teaching hospital in South India. Methods: In this hospital-based cross-sectional method-comparison study, 200 adults underwent IOP measurement by NCT and GAT in the same sitting. The per-patient mean of both eyes was used for analysis. Agreement was evaluated using the paired t-test, Pearson correlation, the intraclass correlation coefficient (ICC) and Bland–Altman limits of agreement, with statistical significance set at p<0.05. Results: The mean age was 52.6 (SD 18.2) years; 109 (54.5%) were men. Mean IOP was 17.47 (SD 2.78) mmHg by NCT and 17.54 (SD 2.89) mmHg by GAT. The mean difference (NCT − GAT) was −0.07 mmHg (SD 0.83), with 95% limits of agreement of −1.70 to +1.56 mmHg; the paired t-test showed no significant systematic difference (p=0.25). Correlation was strong (r=0.957, p<0.001) and agreement was excellent (ICC ≈ 0.96). All paired differences (100%) lay within ±2 mmHg. A non-significant trend toward proportional bias was observed (r=−0.134, p=0.058): NCT read 0.57 mmHg lower at GAT >21 mmHg and 0.29 mmHg higher at GAT <15 mmHg. Conclusion: NCT and GAT demonstrated excellent agreement across the studied IOP range, supporting NCT as a reliable, non-contact screening alternative to GAT in adults. GAT should remain the reference standard for confirmation, particularly at elevated IOP, where NCT showed a slight tendency to under-read.
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